The objective of the Diabetes Prevention Program (DPP) is to prevent or delay the onset of NIDDM among persons at high risk using interventions designed to improve abnormal glucose metabolism. The primary research question of DPP is to determine the safety and efficacy of each of three interventions (intensive lifestyle, metformin and troglitazone) relative to a control intervention (standard lifestyle recommendations) in preventing or delaying the confirmed development of NIDDM.